Exploiting genetic diversity in root phenotypes to overcome soil constraints to potato yields

Although potato growers assiduously prepare the seedbed to promote crop establishment, strong soil can result from the overburden of upper soil layers and/or boom or gun irrigation damaging the ridge. Furthermore, soil strength (assessed as soil penetrometer resistance) increases vertically with soil depth due to (historical) plough pans (below the depth of seedbed preparation) and soil drying (which increases soil strength), which limit root growth. Although potato is traditionally regarded as shallow rooted, selecting varieties better able to grow in strong soil can access soil moisture at depth, sustaining canopy development and photosynthesis and delaying canopy senescence during tuber bulking. Although considerable genetic variation in potato root development exists (Wishart et al. 2013), and root traits conferring increased ability to penetrate strong soil layers have been identified in cereals (Whalley et al. 2013), it is uncertain whether genetic variation in potato root response to strong soil can be exploited.

Individual potato plants will have roots in soils of different moisture contents and strength, and it is uncertain how the plant responds to this spatially heterogeneous environment to regulate canopy growth. Roots in drying soil synthesise chemical signals which are transported to the shoot to regulate canopy development, photosynthesis and senescence, however the contribution of basal (from the seed potato) and stolon-derived roots to this signalling process has not been assessed. This seems critical in regulating crop performance, as these roots show different spatial occupation of the soil profile.

Consequently, the project aims are to determine:
- genetic variation in the ability of basal and stolon-derived roots to penetrate strong soil
- the relative contribution of these root systems to root-to-shoot signalling of strong soil
- whether selecting genotypes based on phenotyping root responses to strong soil can improve the yields / quality of field-grown crops